1. Modify the following SQL command so that the Rep_ID column is the PRIMARY KEY for the table and the default value of Y is assigned to the Comm column. (The Comm column indicates whether the sales representative earns commission.) CREATE TABLE store_reps (rep_ID NUMBER (5), last VARCHAR2 (15), first VARCHAR2 (10), comm CHAR(1)); 2. Change the STORE_REPS table so that NULL values can't be entered in the name columns (First and Last). 3. Change the STORE_REPS table so that only a Y or N can be entered in the Comm column. 4. Add a column named Base_salary with a datatype of NUMBER(7,2) to the STORE_REPS table. Ensure that the amount entered is above zero. 5. Create a table named BOOK_STORES to include the columns listed in the following chart. 6. Add a constraint to make sure the Rep_ID value entered in the BOOK_STORES table is a valid value contained in the STORE_REPS table. The Rep_ID columns of both tables were initially created as different datatypes. Does this cause an error when adding the constraint? Make table modifications as needed so that you can add the required constraint